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In fluid dynamics, disk loading or disc loading is the average pressure change across an actuator disk, such as an airscrew. Airscrews with a relatively low disk loading are typically called rotors, including helicopter main rotors and tail rotors; propellers typically have a higher disk loading. The V-22 Osprey tiltrotor aircraft has a high disk loading relative to a helicopter in the hover mode, but a relatively low disk loading in fixed-wing mode compared to a turboprop aircraft. ==Rotors== Disc loading of a hovering helicopter is the ratio of its weight to the total main rotor disc area. It is determined by dividing the total helicopter weight by the rotor disc area, which is the area swept by the blades of a rotor. Disc area can be found by using the span of one rotor blade as the radius of a circle and then determining the area the blades encompass during a complete rotation. When a helicopter is being maneuvered, its disc loading changes. The higher the loading, the more power needed to maintain rotor speed. A low disc loading is a direct indicator of high lift thrust efficiency.〔Maisel, Martin D., Demo J. Giulianetti and Daniel C. Dugan. (NASA SP-2000-4517, "The History of the XV-15 Tilt Rotor Research Aircraft: From Concept to Flight" (PDF) ) p2. ''NASA'', 2000. Accessed: 17 March 2012.〕 Increasing the weight of a helicopter increases disk loading. For a given weight, a helicopter with shorter rotors will have higher disk loading, and will require more engine power to hover. A low disk loading improves autorotation performance in rotorcraft.〔Leishman, J. Gordon. "(Development of the Autogiro : A Technical Perspective )" page 5. ''Hofstra University'', New York, 2003. 〕 Typically, an autogyro (or gyroplane) has a lower rotor disc loading than a helicopter, which provides a slower rate of descent in autorotation.〔 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Disk loading」の詳細全文を読む スポンサード リンク
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